Determination of cyclosporin A in whole blood by high-performance liquid chromatography using automated column switching.

A fully automated high-performance liquid chromatographic column-switching system is presented for the determination of cyclosporin A in whole blood. After blood proteins were precipitated with acetonitrile, the supernatant was automatically loaded on to a cyanopropyl column for initial separation, and then the fraction containing cyclosporin A was loaded on to a trimethylsilica column for final separation and quantitation. Cyclosporin A was detected by ultraviolet absorption at 205 nm. The minimum detectable concentration of cyclosporin A was 5 ng/ml in 100 microliter of blood. The coefficient of variation of the method was 1.755, 1.748 and 0.655% in whole blood when spiked at the 170, 425 and 850 ng/ml levels, respectively. One assay was completed in 15 min.